The present invention relates to a bobbin changer apparatus for automatically changing or replacing a bobbin case, containing a lower thread bobbin, mounted in a rotary hook of a sewing machine.
Lower thread change apparatus are arranged to, when a bobbin, contained in a bobbin case mounted in a rotary hook supported on a rotary hook base, has run out of a lower thread, automatically replace the empty bobbin case with a new or replacement bobbin case containing a bobbin with a sufficient supply of lower thread thereon, and such lower thread change apparatus have been commonly known as “bobbin changers” or “bobbin changer apparatus” (e.g., Japanese Patent Application Laid-open Publication No. HEI-8-196766 which will hereinafter be referred to as “Patent Literature 1”). Further, in Japanese Patent Application Laid-open Publication No. 2000-157774 (hereinafter referred to as “Patent Literature 2”), there is disclosed a multi-head sewing machine equipped with a plurality of machine heads, where a bobbin changer is provided for each of the machine heads (i.e., for each of rotary hook bases) and drive mechanisms of the individual bobbin changers are drivable via a same or common drive source.
In the bobbin changer disclosed in Patent Literature 2, a bobbin stock section (or bobbin changing cassette) is disposed adjacent to the front end edge of a sewing table closer to a human operator, and a transfer mechanism is provided to reciprocally transfer a bobbin grasping device (or bobbin chuck mechanism) between the rotary hook supported on the rotary hook base located beneath the machine head disposed adjacent to the rear end edge of the sewing table and the bobbin stock section. The bobbin stock section (or bobbin changing cassette) is equipped with a plurality of bobbin cases and receives and delivers bobbin cases to and from (i.e., exchange bobbin cases with) the bobbin changer. Namely, when a thread wound on a lower thread bobbin mounted in any one of the rotary hooks has run short or run out, the bobbin grasping device is moved or transferred, via the transfer mechanism, to the rotary hook in response to a lower thread runout detection signal, takes out, from the rotary hook, the bobbin case containing the empty bobbin, then transferred, via the transfer mechanism, to the bobbin stock section with the taken-out bobbin case grasped by the device, and then delivers the bobbin case to an empty bobbin stock position of the bobbin stock section. After that, the bobbin stock section is rotated through a predetermined angle to allow the bobbin grasping device to take out a new or replacement bobbin case, containing a bobbin with a sufficient supply of lower thread thereon, from another bobbin stock position of the bobbin stock section. Then, the bobbin grasping device is moved, via the transfer mechanism, to the rotary hook with the taken-out new bobbin case held by the device and places the new bobbin case in the empty rotary hook. Bobbin changing operation is automatically carried out generally in accordance with such an operational sequence.
With the bobbin changer of the type disclosed in Patent Literature 2, the human operator only has to perform operation for retrieving an empty bobbin case from the bobbin stock section provided adjacent to the front end edge of the sewing table (machine table) and replenishing or resupplying the bobbin stock section with a new bobbin case containing a bobbin having a sufficient supply of lower thread thereon. Thus, the bobbin changer disclosed in Patent Literature 2 allows the human operator to perform the necessary operation with considerable ease. On the other hand, with the bobbin changer disclosed in Patent Literature 1, where no transfer mechanism is used and the bobbin stock section is disposed near the rotary hook, the human operator itself has to manually change a bobbin case in the rotary hook on the rotary hook base by getting under the sewing table, which is very troublesome operation. Thus, in large-size industrial sewing machines (not only ordinary industrial sewing machines but also embroidery sewing machines), the bobbin changer of the type disclosed in Patent Literature 2 is becoming essential in order to enhance the efficiency of a sewing operation. However, the conventionally-known bobbin changers have much room for improvement, and, in fact, such improvement has been hoped for over the years.
In the bobbin changer disclosed in Patent Literature 2, for example, a guide plate for guiding the movement of the bobbin grasping device has a linear first guide groove, and a second groove having orientation-changing slanted portions near the opposite ends thereof. By being guided by the orientation-changing slanted portions of the second groove, the orientation of a chuck section of the bobbin grasping device can be changed at each end of a transfer stroke of the grasping device. Namely, the transfer mechanism (i.e., guide plate) has integrally incorporated therein a mechanism for changing the orientation of the chuck section at the opposite ends of the transfer stroke.
As well known in the art, the sewing machines come in variety of sizes depending on, for example, the range to be embroidered, and the distance from the rotary hook bases to the front end edge of the sewing table, i.e. from the rotary hooks to the bobbin stock sections, also differs depending on the size of the sewing machine. Thus, guide plates of various types (sizes) would be required which correspond to different distances from the rotary hooks to the bobbin stock sections. With the aforementioned conventional technique (disclosed in Patent Literature 2), where the guide plate has integrally incorporated therein the mechanisms for changing the orientation of the chuck section at the opposite ends of the transfer stroke, it is necessary to separately make such guide plates (having integrally incorporated therein the mechanisms for changing the orientation of the chuck section at the opposite ends of the transfer stroke) in various sizes and constructions suited for various types of sewing machines, which tends to take a lot of time and labor in manufacturing of component parts and therefore results in high cost.
In view of the aforementioned prior art problems, WO2005/047586 (hereinafter referred to as “Patent Literature 3”) discloses a more sophisticated bobbin changer apparatus which includes: a first orientation change mechanism for, during transfer by a transfer mechanism of a bobbin grasping device toward a rotary hook, changing the orientation of a chuck section of the bobbin grasping device so that the chuck section faces toward the rotary hook; and a second orientation change mechanism for, during transfer by the transfer mechanism of the bobbin grasping device toward a bobbin stock section, changing the orientation of the chuck section of the bobbin grasping device so that the chuck section faces toward the bobbin stock section. In the bobbin changer apparatus disclosed in Patent Literature 3, the first and second orientation change mechanisms are detachable from the transfer mechanism.
However, in each of the bobbin changers disclosed in Patent Literature 2 and Patent Literature 3, where the first and second orientation change mechanisms for orientating the chuck section of the bobbin grasping device toward the rotary hook and bobbin stock section, respectively, are provided separately, there would arise the problems that the overall construction of the bobbin changer apparatus becomes complicated and the number of necessary components increases.
Further, because air actuators are used as driving devices for the transfer operation of the transfer mechanism and opening/closing operation of the chuck section of the bobbin grasping device in the conventionally-known bobbin changer apparatus, the drive mechanisms would become extremely complicated in construction and require high cost. Furthermore, in the case where the bobbin changer apparatus is applied to a multi-head sewing machine equipped with a plurality of machine heads, it is difficult to perform control for changing a bobbin of a particular one of a plurality of rotary hooks, because one common drive source is shared among the bobbin changer apparatus corresponding to the rotary hooks.
Furthermore, in the conventionally-known bobbin changer apparatus, there have been taken no appropriate measures against errors in bobbin changing operation. In addition, the conventionally-known bobbin changer apparatus are not constructed to allow a lower thread color change to be effected as desired in the course of sewing of a given sewing pattern.